Inorg. Chem. 2007, 46, 6283−6290
Amine-Controlled Assembly of Metal−Sulfite Architecture from 1D
Chains to 3D Framework
Cristina Austria,† Jian Zhang,† Henry Valle,† Qichun Zhang,§ Emily Chew,† Dan-Tam Nguyen,†
J. Y. Gu,‡ Pingyun Feng,§ and Xianhui Bu*,†
Department of Chemistry and Biochemistry, Department of Physics and Astronomy, California
State UniVersity, Long Beach, 1250 Bellflower BouleVard, Long Beach, California 90840, and
Department of Chemistry, UniVersity of California, RiVerside, California 92521
Received February 19, 2007
Whereas open-framework materials have been made in a variety of chemical compositions, few are known in
which 3-connected SO32- anions serve as basic building units. Here, we report four new metal−sulfite polymeric
structures, (ZnSO3)Py (1, py ) pyridine), (ZnSO3)2(2,2′-bipy)H2O (2, 2,2′-bipy ) 2,2′-bipyridine), (ZnSO3)2(TMDPy)
(3, TMDPy ) 4,4′-trimethylenedipyridine), and (MnSO3)2en (4, en ) ethylenediamine) that have been synthesized
hydrothermally and structurally characterized. In these compounds, low-dimensional 1D and 2D inorganic subunits
are assembled into higher 2D or 3D covalent frameworks by organic ligands. In addition to the structure-directing
effect of organic ligands, the flexible coordination chemistry of Zn2+ and SO32- also contributes to the observed
structural diversity. In compounds 1−3, Zn2+ sites alternate with trigonal pyramidal SO32- anions to form three
types of [ZnSO3]n chains, whereas in compound 4, a 2D-corrugated [MnSO3]n layer is present. Compound 1 features
a rail-like chain with pendant pyridine rings. The π−π interaction between 2,2′-bipy ligands is found between
adjacent chains in compound 2, resulting in 2D sheets that are further stacked through interlayer hydrogen bonds.
Compound 3 exhibits a very interesting inorganic [(ZnSO3)2]n chain constructed from two chairlike subunits, and
such chains are bridged by TMDPy ligands into a 2D sheet. In compound 4, side-by-side helical chains permeate
through 2D-corrugated [MnSO3]n layers, which are pillared by neutral ethylenediamine molecules into a 3D framework
that can be topologically represented as a (3,6)-connected net. The results presented here illustrate the rich structural
chemistry of metal−sulfites and the potential of sulfite anions as a unique structural building block for the construction
of novel open-framework materials, in particular, those containing polymeric inorganic subunits that may have
interesting physical properties such as low-dimensional magnetism or electronic properties.
Introduction
Open-framework and porous solids have found widespread
applications as catalysts, adsorbents, ion-exchangers, and so
forth.1 These important materials have been made in a variety
* To whom correspondence should be addressed. E-mail: [email protected].
† Department of Chemistry and Biochemistry, California State University,
Long Beach.
‡ Department of Physics and Astronomy, California State University,
Long Beach.
§ Department of Chemistry, University of California, Riverside.
(1) (a) Breck, D. W. Zeolite Molecular SieVes; Wiley & Sons: New York,
1974. (b) Flanigen, E. M. In Introduction to Zeolite Science and
Practice; van Bekkum, H.; Flanigen, E. M.; Jansen, J. C., Eds.; Elsevier
Science: New York, 1991; pp 13-34. (c) Wilson, S. T.; Lok, B. M.;
Messina, C. A.; Cannan, T. R.; Flanigen, E. M. J. Am. Chem. Soc.
1982, 104, 1146-1147. (d) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N.
W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003, 423, 705-714.
(e) Palmqvist, A. E. C.; Iversen, B. B.; Zanghellini, E.; Behm, M.;
Stucky, G. D. Angew. Chem. Int. Ed. 2004, 43, 700-704.
10.1021/ic070325h CCC: $37.00
Published on Web 07/10/2007
© 2007 American Chemical Society
of compositions, such as silicates, phosphates, germanates,
borates, phosphites, and sulfides.2-4 Recently, there has been
an increasing interest in the use of 3-connected centers as
basic structural units for the construction of open-framework
materials.5-8 The presence of 3-connected centers has been
(2) (a) Cheetham, A. K.; Ferey, G.; Loiseau, T. Angew. Chem. Int. Ed.
1999, 38, 3268. (b) Zou, X.; Conradsson,; Klingstedt, M.; Dadachov,
M. S.; O’Keeffe, M. Nature 2005, 437, 716-719.
(3) (a) Liao, Y.-C.; Jiang, Y.-C.; Wang, S.-L. J. Am. Chem. Soc. 2005,
127, 12794-12795. (b) Tang, M.-F.; Lii, K.-H. J. Solid State Chem.
2004, 177, 1912-1918.
(4) (a) Feng, P.; Bu, X.; Stucky, G. D. Nature 1997, 388, 735-741. (b)
Bu, X.; Feng, P.; Stucky, G. D. Science 1997, 278, 2080-2085.
(5) Fan, J.; Slebodnick, C.; Troya, D.; Angel, R.; Hanson, B. E. Inorg.
Chem. 2005, 44, 2719-2727.
(6) (a) Johnstone, J. A.; Harrison, W. T. A. Inorg. Chem. 2004, 43, 45674569. (b) Gordon, L. E.; Harrison, W. T. A. Inorg. Chem. 2004, 43,
1808-1809. (c) Harrison, W. T. A. Curr. Opin. Solid State Mater.
Sci. 2002, 6, 407-413.
Inorganic Chemistry, Vol. 46, No. 16, 2007
6283
Austria et al.
recognized to lead to large pore sizes and low framework
density (e.g., -CLO, JDF-20), both of which are desirable
features in porous materials.9
There exist a number of different 3-connected building
blocks, both organic and inorganic. Among inorganic units,
oxoanions are the most common. Such oxoanions include
planar BO33- and CO32- and pyramidal SnO34-, SO32-,
SeO32-, and HPO32-.10-12 Among these 3-connected units,
phosphites are particularly useful for creating open-framework solids. In comparison, little is known about openframework sulfites.13 The work reported here is part of our
systematic exploration of open-framework materials containing 3-connected building units such as phosphites and
sulfites.14-15 It deals with a compositional domain (i.e.,
inorganic-organic hybrid metal-sulfites) about which very
little crystal chemistry is known.
Here, we report four new metal-sulfite polymeric structures, (ZnSO3)Py (1, py ) pyridine), (ZnSO3)2(2,2′-bipy)H2O (2, 2,2′-bipy ) 2,2′-bipyridine), (ZnSO3)2(TMDPy) (3,
TMDPy ) 4,4′-trimethylenedipyridine), and (MnSO3)2en (4,
en ) ethylenediamine) that have been synthesized hydrothermally and structurally characterized. This work represents
an early step toward the exploration of the inorganic-organic
hybrid system based on metal-sulfites. Unlike many metalorganic framework structures in which isolated organic and
inorganic units (0D) are joined into higher-dimensional
frameworks (1D to 3D), these metal-sulfite materials have
a strong tendency to form polymeric inorganic subunits that
are subsequently joined into higher-dimensional structures
through bifunctional organic ligands. The existence of
polymeric inorganic subunits opens the door for the integra(7) (a) Lin, Z.; Zhang, J.; Zheng, S.; Yang, G.-Y. Solid State Sci. 2004,
6, 371. (b) Lin, Z.; Zhang, J.; Zheng, S.-T.; Yang, G.-Y. Eur. J. Inorg.
Chem. 2004, 953. (c) Zhong, Y.-J.; Chen, Y.-M.; Sun, Y.-Q.; Yang,
G.-Y, J. Solid State Chem. 2005, 178, 2613-2619. (d) Zhong, Y.-J.;
Chen, Y.-M.; Sun, Y.-Q.; Yang, G.-Y. Z. Anorg. Allg. Chem. 2005,
631, 1957-1960.
(8) (a) Liang, J.; Li, J.; Yu, J.; Chen, P.; Fang, Q.; Sun, F.; Xu, R. Angew.
Chem. Int. Ed. 2006, 45, 1. (b) Zhang, D.; Yue, H.; Shi, Z.; Feng, S.
Solid State Sci. 2005, 7, 1256.
(9) (a) Baerlocher, C.; Meier, W. M.; Olson, D. H. Atlas of Zeolite
Framework Types; Elsevier: Amsterdam, The Netherlands, 2001. (b)
Huo, Q.; Xu, R.; Li, S.; Ma, Z.; Thomas, J. M.; Jones, R. H.;
Chippindale, A. M. J. Chem. Soc., Chem. Commun. 1992, 875-876.
(10) (a) Gier, T. E.; Bu, X.; Wang, S.; Stucky, G. D. J. Am. Chem. Soc.
1996, 118, 3039. (b) Harrison, W. T. A.; Phillips, M. L. F.; Nenoff,
T. M.; MacLean, E. J.; Teat, S. J.; Maxwell, R. S. J. Chem. Soc.,
Dalton Trans. 2001, 546-549.
(11) (a) Rao, C. N. R.; Behera, J. N.; Dan, M. Chem. Soc. ReV. 2006, 35,
375-387. (b) Ayyappan, S.; Bu, X.; Cheetham, A. K. Chem. Commun.
1998, 2181-2182.
(12) (a) Harrison, W. T. A.; Phillips, M. L. F.; Stanchfield, J.; Nenoff, T.
M. Angew. Chem. Int. Ed. 2000, 39, 3808-3810. (b) Millange, F.;
Serre, C.; Cabourdin, T.; Marrot, J. Ferey, G. Solid State Sci. 2004,
6, 229-233.
(13) (a) Diaz de Vivar, M. E.; Baggio, S.; Munoz, J. C.; Baggio, R. Acta.
Crystallogr. 2005, C61, m30-m33. (b) Long, D. -L.; Kogerler, P.;
Cronin, L. Angew. Chem. Int. Ed. 2004, 43, 1817. (c) Manos, M. J.;
Miras, H. N.; Tangoulis, V.; Woollins, J. D.; Slawin, A. M. Z.;
Kabanos, T. A. Angew. Chem. Int. Ed. 2003, 42, 425. (d) Long, D.
-L.; Abbas, P.; Kogerler, P.; Cronin, L. Angew. Chem. Int. Ed. 2005,
44, 3415.
(14) (a) Chen, L.; Bu, X. Inorg. Chem. 2006, 45, 4654-4660. (b) Chen,
L.; Bu, X. Chem. Mater. 2006, 18, 1857-1860.
(15) (a) Nguyen, D-T.; Bu, X. Inorg. Chem. 2006, 45, 10410-10412. (b)
Nguyen, D.-T.; Chew, E.; Zhang, Q.; Choi, A.; Bu, X. Inorg. Chem.
2006, 45, 10722-10727.
6284 Inorganic Chemistry, Vol. 46, No. 16, 2007
tion of useful physical properties (e.g., low-dimensional
magnetism, electronic conductivity) into these materials. In
the materials reported here, 1D and 2D inorganic subunits
are assembled into 2D and 3D covalent frameworks. The
rich crystal chemistry is a result of the unique structural
directing effect of organic ligands, coupled with variable
coordination chemistry of Zn2+ (or Mn2+) and SO32- building
units.
Experimental Section
Synthesis. (ZnSO3)Py (1). Zinc nitrate hexahydrate (98%,
0.3050 g), ammonium sulfite monohydrate (92%, 0.4028 g),
pyridine (0.2058 g), and distilled water (3.990 g) were mixed
in a 15 mL glass vial, and the mixture was stirred for 20
min. The pH of the mixture was 7.10. The vial was then
sealed and heated at 110 °C for 5 d. The vial was
subsequently allowed to cool to room temperature. The
colorless crystals were obtained in 65% yield. Results of
elemental analysis (in wt %) for 1, C5H5NO3SZn, are 26.29
(calcd 26.75) for C, 2.52 (calcd 2.24) for H, and 6.40 (calcd
6.24) for N.
(ZnSO3)2(2,2′-bipy)H2O (2). Zinc carbonate (0.1582 g),
ammonium sulfite monohydrate (0.1725 g), 2,2′-bipyridine
(0.1543 g), methanesulfonic acid (99.5%, 0.1915 g, used for
the adjustment of pH), ethylene glycol (1.7002 g), and
distilled water (6.2176 g) were mixed in a 23 mL Teflon
cup, and the mixture was stirred for 20 min. The pH value
was 5.43. The vessel was then sealed and heated at 120 °C
for 7 d. The autoclave was subsequently allowed to cool to
room temperature. The plate-shaped transparent colorless
crystals were obtained in 56% yield. Results of elemental
analysis (in wt %) for 2, C10H10N2O7S2Zn2, are 25.98 (calcd
25.83) for C, 2.39 (calcd 2.17) for H, and 5.80 (calcd 6.02)
for N.
(ZnSO3)2(TMDPy) (3). Zinc carbonate (0.1267 g), potassium sulfite (0.2058 g), 4,4′-trimethylenedipyridine
(0.3000 g), acetic acid (0.1401 g, used for the adjustment of
pH), ethylene glycol (2.0223 g), and distilled water
(6.2188 g) were mixed in a 23 mL Teflon cup, and the
mixture was stirred for 20 min. The pH value was 6.13. The
vessel was then sealed and heated at 120 °C for 7 d. The
autoclave was subsequently allowed to cool to room temperature. The plate-shaped transparent colorless crystals were
obtained in 67% yield. Results of elemental analysis (in wt
%) for 3, C13H13N2O6S2Zn2, are 32.15 (calcd 31.99) for C,
2.60 (calcd 2.68) for H, and 5.49 (calcd 5.74) for N.
(MnSO3)2en (4). Manganese nitrate hydrate (98%, 0.277
g), ammonium sulfite monohydrate (0.408 g), and 6 g of
water were mixed in a vial for 10 min. Then, ethylenediamine
(0.100 g) was added to the above mixture and stirred for
another 10 min. The pH of the resulting mixture was 9.40.
The vessel was sealed and heated at 110 °C for 4 days. After
cooling to room temperature, clear orange-brown needleshaped crystals were obtained in 45% yield. Results of
elemental analysis (in wt %) for 4, CH4NO3SMn, are 6.85
(calcd 7.28) for C, 2.12 (calcd 2.44) for H, and 8.61 (calcd
8.49) for N.
Amine-Controlled Assembly of Metal-Sulfite Architecture
Table 1. Summary of Crystal Data and Refinement Results
complexes
1
2
3
4
empirical formula
structural formula
fw
temp (K)
A (Å)
B (Å)
C (Å)
β (deg)
V (Å3)
Z
space group
2θmax (deg)
total data
unique data
data, I > 2σ(I)
params
R(F) (I > 2σ(I))
Rw(F 2)(I > 2σ(I))
GOF
C5H5NO3SZn
(ZnSO3)py
224.53
293
4.9404(3)
8.7820(5)
17.1114(9)
96.395(4)
737.79(7)
4
P21/c
42
6395
745 [R(int) ) 0.0563]
556
100
0.0331
0.0760
1.095
C10H10N2O7S2Zn2
(ZnSO3)2(2,2′-bpy)H2O
465.06
293
14.1016(10)
12.4216(8)
8.5128(6)
105.538(3)
1436.64(17)
4
P21/c
71
39891
6006 [R(int) ) 0.0245]
4713
208
0.0261
0.0713
1.125
C13H13N2O6S2Zn2
(ZnSO3)2(TMDPy)
488.11
293
10.56520(10)
9.64940(10)
17.0340(2)
102.6820(10)
1694.21(3)
4
P21/n
48
25145
2749 [R(int) ) 0.0842]
2145
226
0.0302
0.0747
0.954
CH4NO3SMn
(MnSO3)2en
165.06
293
15.7400(6)
4.8958(2)
5.9311(2)
90.00
457.05(3)
4
Pnnm
72
11022
1072[R(int) ) 0.0210]
998
41
0.0178
0.0507
1.193
Thermal Analysis. The thermogravimetric analysis was
performed on a TA Instruments SDT Q600 under a flowing
nitrogen atmosphere. The flow rate of the nitrogen gas was
controlled at about 100 liters per minute. A total of
5.6090 mg of 1, 9.3120 mg of 2, 7.3890 mg of 3, and
29.5120 mg of 4 were heated between room temperature and
1000 °C at a heating rate of 5 °C/min.
X-ray Powder Diffraction. X-ray powder diffraction
experiments were performed on a Bruker D8 Advance X-ray
powder diffractometer operating at 40 kV and 40 mA (Cu
KR radiation, λ ) 1.5418 Å). Data collection was carried
out with a step size of 0.03 degrees and a counting time of
1 s per step. The 2-theta angular range is from 5 to 40
degrees.
Single-Crystal Structure Analysis. Each crystal was
glued to a thin glass fiber with epoxy resin and mounted on
a Bruker APEX II diffractometer equipped with a fine focus,
2.0 kW sealed-tube X-ray source (Mo KR radiation, λ )
0.71073 Å) operating at 50 kV and 30 mA. The empirical
absorption correction was based on equivalent reflections,
and other possible effects such as absorption by the glass
fiber were simultaneously corrected. Each structure was
solved by direct methods followed by successive difference
Fourier methods. All non-hydrogen atoms were refined
anisotropically. Computations were performed using SHELXTL, and final full-matrix refinements were against F 2. The
crystallographic results are summarized in Table 1.
(ZnsN 2.055(6) Å). Within the ZnSO3 double chain, two
Zn atoms and two S atoms (from two sulfite anion) form a
4-membered ring (Zn2S2, not counting four bridging oxygen
sites). Such 4-membered rings extend in two directions to
form the ZnSO3 double chain through the edge-sharing of
4-ring units.
Thermal analysis shows that compound 1 is stable until
approximately 180 °C, which is the onset temperature for a
gradual weight loss of 65.6% between 180 and 800 °C.
Because the weight percentage of the organic component is
only 35.23%, the loss of pyridine is also accompanied by
the loss of SO2 (calcd 28.51%). The total experimental weight
loss is about 1% lower than the calculated value of 36.3%
for the decomposition of (ZnSO3)Py into ZnO.
(ZnSO3)2(2,2′-bipy)H2O (2): An Inorganic Double
Chain from Alternating 3- and 4-Membered Rings. In
compound 2, Zn2+ ions are also bridged by SO32- anions to
form an infinite neutral double chain along the c axis.
However, the bonding pattern in compound 2 is dramatically
different from that in compound 1, illustrating the structural
diversity that can be achieved in the Zn-SO32- system. As
shown in Figure 2, there are two independent Zn2+ ions with
different coordination geometry. Zn1 is tetrahedrally coor-
Results and Discussion
(ZnSO3)Py (1): A Rail-Like Inorganic ZnSO3 Double
Chain with Pendant Organic Ligands. In compound 1,
Zn2+ and SO32- form an infinite neutral rail-like double chain
along the a axis. As shown in Figure 1, all of the Zn2+ ions
in the ZnSO3 double chain are tricoordinated to three O atoms
of three different SO32- units, and each SO32- unit connects
to three Zn2+ ions. Thus, both Zn2+ and SO32- serve as threeconnected centers. The distances between adjacent Zn-Zn
centers are 3.832(1), 4.001(1), and 4.940(1) Å, respectively.
Each neutral pyridine ligand binds to one Zn2+ ion via its N
site, which completes the fourth coordination of Zn2+ ions
Figure 1. Rail-like chain in complex 1. Purple, Zn; Yellow, S; Red, O;
Blue, N; Gray, C.
Inorganic Chemistry, Vol. 46, No. 16, 2007
6285
Austria et al.
Figure 2. Double chain in complex 2. Hydrogen bonds were shown as dashed lines. Purple, Zn; Yellow, S; Red, O; Blue, N; Gray, C.
dinated by four O atoms coming from four different SO32anions. In contrast, Zn2 has distorted octahedral coordination
geometry and is bonded by three O atoms coming from only
two different SO32- anions. The three remaining coordination bonds of Zn2 are made to one aqua O atom and two N
atoms of the same 2,2′-bipy ligand. It is worth noting that
Zn1 and Zn2 share one common oxygen site from a SO32group.
The structural complexity of compound 2 is further
increased by the occurrence of two independent and coordinatively different SO32- anions. Whereas both of them use
all three O atoms to connect to three Zn2+ ions, their bonding
modes are not the same. One SO32- group (S2) is connected
to three Zn2+ sites with all of the oxygen sites bicoordinated
between the Zn2+ and S4+ sites, similar to the bonding pattern
in compound 1. On the other hand, in the other SO32- group
(S1), one oxygen site is tricoordinated between two Zn2+
sites and one S4+ site. The Zn-O-Zn linkage allows the
formation of the 3-membered ring (Zn1, Zn2, and S2, with
three bridging oxygen sites not counted). The 4-membered
ring is formed between two crystallographically identical Zn1
sites, one S1 site, and one S2 site. These 3- and 4-membered
rings alternate to form a wavy double chain.
The 2,2′-bipy ligands chelate the Zn2 sites and are located
at two sides of the double chain with molecular planes
parallel to one another. Along the same side, the distance
between the two adjacent 2,2′-bipy ligands is 8.513 Å. The
gap is so wide that the 2,2′-bipy ligand from the adjacent
chain partially fills the gap, as shown in Figure 3. Weak
π-π interactions are found between two pyridine rings of
two 2,2′-bipy ligands with a center-to-center distance of
3.638 Å. Such π-π interactions result in the formation of a
layer parallel to the bc plane.
It is interesting to note that the aqua ligand forms two
types of hydrogen bonds. One is the intrachain hydrogen
bond (O1W‚‚‚O6 ) 2.7919(19) Å), and another is the
interchain hydrogen bond (O1W‚‚‚O2i ) 2.7892(17) Å;
symmetry code: i ) -x + 1, -y + 1, -z + 1). Two adjacent
layers are linked face-to-face by interchain hydrogen bonds,
forming a double-layer structure (Figure 4). The further
6286 Inorganic Chemistry, Vol. 46, No. 16, 2007
Figure 3. Space-filling view of two 2,2′-bipy ligands and the π-π
interactions in complex 2. Purple, Zn; Yellow, S; Red, O; Blue, N; Gray,
C.
stacking of such double layers leads to the observed crystal
structure. The interactions between double layers are assumed
to be van der Waals forces.
Thermal analysis of compound 2 shows two steps of
weight losses. The first weight loss occurs between 50 and
200 °C with an observed weight loss of 3.46% corresponding
to the loss of the water molecules (calcd 3.87%). The second
weight loss of 63.04% occurs in the range of 225-945 °C,
which can be attributed to the elimination of 2,2′-bipy (calcd
33.55%) and SO2 (calcd 27.53%). The remaining weight of
33.5% is likely that of ZnO (calcd 35.06%).
(ZnSO3)2(TMDPy) (3): From 1D Inorganic Chain to
2D Inorganic-Organic Hybrid Layers. Compound 3 also
contains inorganic ZnSO3 chains, but it is very different from
chains in compounds 1 and 2. As shown in Figure 5, two
independent Zn2+ ions (Zn1 and Zn2) and two independent
SO32- anions alternate to form an infinite chain along the b
direction. Two independent SO32- anions have the same
Amine-Controlled Assembly of Metal-Sulfite Architecture
Figure 4. 3D stacking structure of complex 2. Hydrogen bonds were
shown as dashed lines. Purple, Zn; Yellow, S; Red, O; Blue, N; Gray, C.
Figure 5. View of a chain containing two types of chairlike dimeric units
in complex 3. Purple, Zn; Yellow, S; Red, O.
coordination mode as that in the complex 2, and both of
them use all three O atoms to connect to three Zn2+ ions.
On the other hand, the bonding modes of two Zn2+ sites
differ from those observed in compounds 1 and 2. Two Zn2+
ions have tetrahedral (Zn2) and distorted square-pyramidal
geometries (Zn1), respectively.
Two symmetry-related SO32- anions (S1) coordinate to
two Zn1 centers with a Zn-Zn distance of 3.610 Å, which
leads to the formation of a chairlike dimeric unit. In
comparison, two symmetry-related SO32- anions (S2) bridge
two Zn2 centers, which also lead to the formation of a
chairlike dimeric unit, distinctly different from the dimeric
unit formed by Zn1 and S1 sites. The Zn-Zn distance within
the second type of dimer is slightly shorter (3.489 Å). These
two types of chairlike dimeric units are linked through a
3-ring unit (-S2-O-Zn1-O-Zn2-O) into an infinite
inorganic chain (Figure 5).
Each Zn site has an available bond for connection with
the organic ligand, and each TMDPy ligand joins together
two independent Zn sites (Zn1 and Zn2) of two adjacent
chains through the Zn-N bond (Zn1-N2 ) 2.052(2) and
Zn2-N1 ) 2.024(2) Å). The distance between two TMDPyconnected Zn sites is 13.953 Å. A 2D sheet that is parallel
to the ab plane is formed (Figure 6).
Thermal analysis shows that compound 3 is stable until
approximately 220 °C, which is the onset temperature for a
gradual weight loss of 66.9% between 250 and 975 °C.
Because the weight percentage of the organic component is
only 40.57%, the loss of TMDPy is also accompanied by
the loss of SO2 (calcd 26.23%). The total experimental weight
loss is about 0.3% lower than the calculated value of 33.4%
for the decomposition of (ZnSO3)2(TMDPy) into ZnO.
(MnSO3)2en (4): A 3D Framework by Pillaring HelixContaining Layers. In compound 4, Mn2+ and SO32- form
infinite neutral 2D layers that are crosslinked into a 3D
framework by ethylenediamine molecules through Mn-N
bonds. Within the MnSO3 layer, Mn2+ and O2- (from the
sulfite anion) form an approximately square grid-type
structure (Mn4O4) (Figure 7). Each Mn2+ is bonded to five
oxygen atoms of four separate SO32- groups (two oxygen
sites from a single SO32- group and three other oxygen sites
from three separate SO32- groups). Each SO32- group is in
turn connected to four Mn2+ sites with one oxygen site
bicoordinated between one Mn2+ and one S4+ site and two
oxygen sites tricoordinated between two Mn2+ and one S4+
sites. In other words, two oxygen atoms of the SO32- anion
form a bridging mode across two Mn2+ sites with an MnMn distance of 3.896 Å. Such tricoordinated O atoms link
Mn2+ sites to form left- and right-handed helices along the
b axis. The left- and right-handed helices are not intertwined
together. Instead, they are arranged side-by-side along the c
direction.
Within the MnSO3 layer, the S4+ site and two tricoordinated O atoms of the SO32- anion behave as 3-connected
nodes, and the Mn2+ sites act as 5-connected nodes. The
layer can be topologically represented as a 2D (3,5)connected plane. The coordination environment of each Mn2+
site is completed by the N atoms of the ethylenediamine
ligand and exhibits distorted octahedral geometry. Ethylenediamine molecules on two adjacent Mn2+ sites are distributed
on opposite sides of the layer (Figure 8), which serves to
cross-link adjacent neutral MnSO3 layers into a 3D framework (Figure 9). When the bridging ethylenediamine molecules are taken into consideration, each Mn2+ site becomes
6-connected, and the whole framework is thus a 3D (3,6)connected net.
Thermal analysis shows that compound 4 is stable until
approximately 200 °C, which is the onset temperature for a
gradual weight loss of 52.9% between 200 and 690 °C.
Because the weight percentage of the organic component is
only 18.45%, the loss of ethylenediamine is also accompanied by the loss of SO2 (calcd 38.81%). The total
experimental weight loss is about 4% lower than the
calculated value of 57.3% for the decomposition of (MnSO3)2en into MnO.
Inorganic Chemistry, Vol. 46, No. 16, 2007
6287
Austria et al.
Figure 6. 2D layer in complex 3 viewed down the c axis. Purple, Zn; Yellow, S; Red, O; Blue, N; Gray, C.
ferrimagnetic behavior. The decrease of χmT below 13 K
results from a saturation of the χm value and/or the zerofield splitting effect. Because the Mn(SO3) layers in 4 are
well separated by the en bridges, the ferrimagnetic behavior
can be suggested to arise from intralayer magnetic interactions. The magnetic susceptibility above 22 K obeys the
Curie-Weiss law (1/χm ) (T-Θ)/C) with the Curie constant,
C, of 4.93 cm3 K mol-1 and a negative Weiss constant, Θ,
of -34.86 K, which also indicates an intralayer antiferromagnetic coupling between the adjacent Mn(II) ions through
the SO3 bridges.
Figure 7. Top, the infinite MnSO3 layer in complex 4 viewed down the
a axis; bottom, the layer viewed down the b axis, showing left and right
helices. Purple, Mn; Yellow, S; Red, O.
The magnetic susceptibility of 4 was measured in the range
2-300 K at 5000 Oe (Figure 10). The χmT value of each
Mn unit (4.45 cm3 K mol-1) at 300 K is almost equal to that
(4.37 cm3 K mol-1) expected for one magnetically isolated
high-spin Mn(II) ion. Upon cooling, χmT decreases smoothly
to a minimum (1.99 cm3 K mol-1) at 22 K, indicating the
presence of a dominant antiferromagnetic interaction. Then,
it increases rapidly as the temperature decreases to 13 K (χmT
value ) 2.71 cm3 K mol-1). These features are indicative of
6288 Inorganic Chemistry, Vol. 46, No. 16, 2007
Structural Variations, Comparisons, and Trends. From
the above structural descriptions, it is clear that metal ions
and SO32- anions can form unique inorganic subunits that
can be chains or layers. The large structural variations are
closely associated with the flexible coordination chemistry
of SO32- and metal cations. Within these structures, the
oxygen atoms in the SO32- anion exhibit two types of
bonding modes: (I) the bicoordination mode between one
metal site and one sulfur site as in 1, 2, 3, and 4; and (II)
the tricoordination mode between two metal sites and one
sulfur site as in 2, 3, and 4. Such bonding modes have been
observed before in other sulfites such as [Zn2(SO3)2(C12H12N2)(H2O)]n and [Zn2(SO3)2(C12H12N2)2]‚2H2O.13 Bonding mode
II is much less common in phosphites, which accounts for
the observed structural differences between these sulfites and
similarly prepared phosphites.
The four polymeric materials possess combinations of
bonding types I and II in different ratios. In compound 1,
only type I is observed (I to II ratio ) 100:0), whereas in
compounds 2 and 3, only one oxygen site on the S1 site is
type II, and five other oxygen sites (two on the S1, three on
S2) are type I (I to II ratio ) 83.3:16.7). In contrast,
compound 4 has a much higher percentage of the type II
mode, with two oxygen sites being type II and only one
oxygen site being type I (I to II ratio ) 33.3:66.7). Thus,
Amine-Controlled Assembly of Metal-Sulfite Architecture
Figure 8. (a) Ethylenediamine ligands are located at two sides of the layer. (b) The schematic representation of the (3,5)-connected plane in complex 4;
solid circles and open circles represent two different bonding directions of the ethylenediamine ligands.
Figure 9. Viewed down the b axis, the infinite MnSO3 sheets are pillared by neutral ethylenediamine molecules into a 3D open framework in (MnSO3)2en.
Purple, Mn; Yellow, S; Red, O; Blue, N; Gray, C.
there is a progressive increase in the type II bonding mode
from 1 to 4.
Another structural feature in these sulfites is the chelating
bonding mode, which is rarely found in phosphites. In
compounds 2 and 3, two oxygen sites (types I and II) of the
same sulfite group bind to the same metal site. In comparison,
in compound 4, two oxygen sites (both type II) of the same
sulfite group bind to the same metal site.
Parallel to the coordination variations of SO32-, the metal
site in these polymeric structures also displays different
coordination geometry. In compound 1, all of the metal sites
(Zn2+) are tetrahedrally coordinated, whereas in compound
2, octahedrally coordinated Zn2+ sites coexist with tetrahedrally coordinated Zn2+ sites. Compound 3 has a unique
combination between pentacoordinated Zn2+ sites and tetrahedrally coordinated Zn2+ sites. All of the metal sites
(Mn2+) in compound 4 are octahedrally bonded because of
the stronger preference for the octahedral coordination by
Mn2+.
The interplay of these coordination features of metal sites
and SO32- results in neutral inorganic units with alternating
metal sites and SO32- anions. Such inorganic subunits of
different dimensionality (1D and 2D) are subsequently
connected into extended frameworks of higher dimensionality
(2D and 3D) by using bifunctional organic ligands, as in
compounds 3 and 4. In comparison, metal phosphites are
more likely to form negatively charged polymeric units from
1D to 3D with protonated amine molecules as extraframework charge-balancing species. So far, no 2D or 3D metalsulfite frameworks that encapsulate protonated organic
amines have been prepared, which highlights the different
crystal chemistry between sulfites and phosphites.
Conclusion
This work reports four new inorganic-organic hybrid
structures based on metal-sulfite chains and layers. The
tendency of the metal-sulfite system to form polymeric
inorganic units is different from commonly observed metalInorganic Chemistry, Vol. 46, No. 16, 2007
6289
Austria et al.
Figure 10. 1/χm and χmT versus T plot with the theoretical fit (-) for compound 4.
organic frameworks that are dominated by structures with
isolated inorganic and organic units. Because of the occurrence of the polymeric inorganic unit, the metal-sulfite
system illustrated here has the potential to help develop
framework materials with unique physical properties such
as low-dimensional magnetism and electronic properties that
are characteristic of inorganic materials. It is clear from the
results reported here that the inorganic-organic hybrid
metal-sulfite system is very unique, and its crystal chemistry
cannot be extrapolated from earlier studies of other related
systems such as metal phosphites. Its potential to be used in
the construction of crystalline open-framework materials
awaits further synthetic and structural exploration.
Acknowledgment. We thank the support of this work
by NIH (X.B., Grant 2 S06 GM063119-05), NSF-MRI
6290 Inorganic Chemistry, Vol. 46, No. 16, 2007
(Y.Y.G. and X.B.), the NIH-RISE program (X.B.), Research
Corporation (X.B., Grant CC6593), the donors of the
Petroleum Research Fund (administered by the ACS) (X.B.,
Grant 41382-GB10), and the National Science Foundation
(P.F.).
Supporting Information Available: Crystallographic data
including positional parameters, thermal parameters, bond distances
and angles (CIF), ORTEP diagrams, experimental and simulated
X-ray powder patterns, and TGA plots for compounds 1-4. This
material is available free of charge via the Internet at http://
pubs.acs.org.
IC070325H